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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

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tation may correspond to the interior flats described in several of the Yakutat Bay glaciers.
The lateral moraine on the eastern side of the glacier, mentioned by Gilbert, is one of the best developed deposits of this sort which we have seen in Alaska (PL CXXXTTI). It is a narrow-crested ridge 30 to 50 feet high and with so sharp a crest that it is difficult to walk upon it. On the western side of this ridge is a bare slope of ground moraine and bed rock extending to the shores of the cove, and to the present border of the glacier; on the eastern side it is bordered by dense mature forest. This lateral moraine is a conspicuous object in the region, curving northward along the margin of Serpentine Glacier for a distance of over a mile, beyond which it could not be seen from sea level. There is a less conspicuous lateral moraine above the western border of the glacier near the terminus, and extending a short distance up the valley. There is also a well developed moraine between the main glacier and the large tributary on the west.
The barren zone, previously noted by Grant and Higgins, comprises all of the area between these lateral moraines, the terminal moraine, and the glacier. It has been covered so recently by the ice that there are only scattered shrubs on the surface, most of the alders being 23 to 27 years old, while the oldest spruce seen had 26 annual rings.
There is an older terminal moraine outside the one described above, the only remnant of it being preserved southwest of the glacier where it is very hummocky, and includes many large bowlders. This moraine rises to a height of approximately 50 or 75 feet and has a wedge-shape (Fig. 45) with the point of the wedge on the shore of Harriman Fiord, whence it broadens westward, in a half mile attaining a width of 2000 feet. Probably this wedge-shape is due to the fact that the eastern portion of the older moraine was destroyed by the recent advance already described. That t.hia outer moraine was made long before the inner moraine is proved by the presence of older trees upon it, there being a thick growth of willow and alder and many spruces and hemlocks nearly a century old. The oldest tree examined was a foot in diameter and had 93 annual rings. The forest on this older moraine is, however, younger and less open than the normal mature forest, such as that outside the lateral moraine to the east of the glacier.
Outwash. The southern side of the older terminal moraine is flanked by a narrow strip, or apron, of outwash gravel and beach deposits, less than one-eighth of a mile wide at low tide, and only 200 to 350 feet wide at high tide. The vegetation proves that most of this outwash gravel flat is associated in origin with the older advance. Most of it is covered with grass, but there are scattered groups of mature trees upon its surface.
Crossing this older terminal moraine, and covering parts of the low, undulating surface of the inner moraine, is a small area of outwash gravel, built from the present ice front. Since until recently streams have flowed over it and it has been undetermined by slumping, there is little vegetation on its surface, the oldest shrubs observed being but 8 years old. Two conspicuous stream-cut channels extend from this inner area of outwash gravels across the older terminal moraine and outwash apron to the sea. They are 1300 and 2000 feet in length, respectively, and where they cross the outer moraine are from 50 to 300 feet in width. Each of them is now abandoned and they were evidently formed at the time of the last advance, when the ice partly destroyed the older terminal moraine and when the glacial streams flowed across the older moraine. In the bottoms of these channels are stream-borne gravels, and abandoned terraces. The scat-